Joy from the soul's revelation

הד' מינים מביאים השמחה כמ"ש ולקחתם כו' ושמחתם.

The four species bring joy, as it says, "And you shall take… and you shall rejoice" (Vayikra 23:40).

The mitzvah of the daled minim is connected to simchah, for the pasuk juxtaposes taking the species with rejoicing before Hashem.

ובאמת עיקר השמחה בהתגלות כח הנשמה.

And in truth, the essence of joy lies in the revelation of the power of the neshamah.

True simchah comes when the inner power of the soul is uncovered and shines forth.

וע"י המינים מתקשרים בנר"נ כמ"ש ולידע איך שמך נקרא עלי.

And through the species one becomes bound to the nefesh, ruach, and neshamah, as it says, "and to know how Your name is called upon me."

Taking the four species connects a person to all the levels of his soul (nefesh, ruach, neshamah), allowing him to recognize how Hashem's name rests upon him.

וכמ"ש בזוה"ק בפסוק כל הנקרא בשמי כו'.

As is taught in the Zohar HaKadosh on the pasuk, "all that is called by My name…" (Yeshayahu 43:7).

The Zohar explains that the soul is "called by Hashem's name," and the mitzvah of the minim awakens this awareness of the soul's Divine source.

ולכן בשבת קודש דיש נשמה יתירה השמחה בעצם היום וא"צ לעורר השמחה ע"י המינים.

Therefore on Shabbos Kodesh, when there is a neshamah yeseirah (additional soul), the joy is in the very day itself, and there is no need to awaken the joy by means of the species.

On Shabbos a person already receives an extra soul, so the simchah is intrinsic to the day and requires no external arousal — which is why the daled minim are not taken on Shabbos.

וכן שמעתי מאמו"ז ז"ל לענין מ"ש התוס' [להוכיח] משבת דאי אפשר לקיים שלמי שמחה דבעי זביחה בשעת שמחה.

And so I heard from my grandfather, of blessed memory, regarding what Tosafos wrote — to prove from Shabbos that it is impossible to fulfill the shelamim of simchah, which require slaughtering at the time of rejoicing.

The Sefas Emes cites a teaching from his grandfather (the Chiddushei HaRim) on a Tosafos that uses Shabbos to show one cannot bring the festive shelamim offering, since its shechitah would have to take place at the time of rejoicing — yet shechitah is forbidden on Shabbos.

(ע"ש בר"ה ד' ה').

(See there in Rosh Hashanah, daf 5.)

The Sefas Emes gives the reference for this Tosafos in Maseches Rosh Hashanah, page 5.

[ואמר] דבשבת יש שמחה בעצם היום אפילו בלי שלמים כמ"ש חז"ל בפסוק וביום שמחתכם אלו השבתות עכ"ד.

[And he said] that on Shabbos there is joy in the very day itself, even without the shelamim, as Chazal taught on the pasuk "and on the day of your rejoicing" — these are the Shabbosos. End of his words.

His grandfather resolved that on Shabbos one does not need the simchah-offering at all, because the day itself contains joy, as Chazal expound that "the day of your rejoicing" (Bamidbar 10:10) refers to Shabbos.

והטעם נכון כמ"ש דהארת הנשמה יתירה מביא השמחה:

And the reason is well-founded, as explained: that the illumination of the neshamah yeseirah brings the joy.

The Sefas Emes confirms his grandfather's point with his own idea: the light of the extra Shabbos soul is itself the source of the day's simchah, so no external mitzvah is needed to generate it.

Summary: The four species of Sukkos bring simchah by connecting a person to the inner power of his soul, since true joy flows from the revelation of the neshamah. On Shabbos, however, one already receives a neshamah yeseirah, so the joy is intrinsic to the day and needs no external arousal. The Sefas Emes supports this with his grandfather's teaching that on Shabbos one cannot — and need not — bring the simchah-offering, because "the day of your rejoicing" itself refers to Shabbos, whose extra-soul light is the very source of its joy.